Many athletes earn catchy nicknames from other team members; indeed, these friendly nicknames can promote a feeling of team unity.
Explanation:
The third option is the correct one because the semicolon acts as a stop that signals the end of the first sentence. The word "indeed" is a linking word that connects the first independent clause with the second one. Also, when we use the word indeed in this way, it has to be followed by a colon.
